Magnetic process control



March 25, 1952 c, DEVOL MAGNETIC PROCESS CONTROL Filed April s, 194e 2 SHEETS-SHEET l INVEN TOR. GEORGE C. DE vol.

ATTY.

March 25, 1952 G. c. DEvol.

MAGNETIC PROCESS CONTROL 2 SHEETS-SHEET 2 xl u ma /06" W Y INVENTOR.

GEORGE C, DEVO/ F/G. 7 By ATTY.

Patented Mar. 25, 1952 MAGNETIC PROCESS CONTRL George C. Devel, Greenwich, Conn., assigner to Remington Rand Inc., New York, N. Y., acorporation of Delaw .re

Appiication April 3, 1946, Serial No. 659,223

23 Claims. 1

This invention relates to a system for controlling the operation of a wide variety of different devices, such as machine tools, trafdc lights, and the mechanisms for eiecting the steps in a process. It aims at providing new and improved means for establishing an arbitrary, operational time-sequence, and for this purpose presents advantages over mechanical cams and photo-electric devices heretofore in similar use.

Apparatus embodying my invention includes a sensing element, a controlling element having magnetically diierent parts, means for causing relative movement between those elements, and a detector diierently responsive to the coaction of the sensing means with the magnetically different parts of the controlling element. A source of sustained or verving magneto-motive force or combination of magneto-motive forces is contained in the sensing element or in the controlling element, or in bot-h. The detector is responsive to the eiect of the magneto-motive force or forces in the :flux path linking the sensing element and that portion of the controlling element which is opposite the sensing element at any given time. lThe resulting control will vary with time in dependence on changed detector output as dissimilar portions of the controlling element are brought into apposition with the sensing element. Significantly, the control effected by the detector depends not on the rateof-change in the interaction between the controllinfr element and the sensing element during their relative travel, but on the actual change in that interaction. The nature of the control effected does not depend on the rate of relative travel and would be sustained `even were the travel interrupted.

The controlling element interacts with the sensing element in either of two fundamental ways, which in certain embodiments of the invention are indistinguishable. In one embodiment the controlling element is of magnetic material, the successively sensed portions of which are or may be magnetized differently and are of uniform cross-section, in another embodiment the successively portions of the controlelement are ci 'iiagi ctie material of varying cross-section, and are magnetized uniformly or are unmagnetiri fi. n convenience, the differences of either type between successive parts oi the controlling element are termed magnetic dierences.

The detector is arranged in diierent ways to produce various desired controls. One form of controlling element magnetic dierences along an invariable sensing path, and these differences cause the desired control by varying the detector output. In another form the controlling member contains an arbitrary pattern or contour which is magnetically uniform along the contour but which contrasts with the material adjacent the outline. The magnetic differences which cause changing detector output during the relative travel of the sensing and controlling elements generally along the contour are utilized to control a servo system which displaces the sensing element relatively toward the outline so as to maintain uniform detector output. In this system the mechanical output of the servo motor is relied upon for eiecting the desired external control.

In that aspect of the invention having a regular, invariable sensing path, that form of controlling element is preferred which has D.C. magnetization at crit-ical portions of the path. Apparatus incorporating such a controlling element may be combined to great advantage with equipment where that element must be in a remote or inaccessable location and where quick changes of the cycle may be required. Unlike known controls, the control provided by my invention can be readily obliterated and it can be quickly renewed to meet changed arbitrary requi 'ements The invention and further features of novelty `will be better appreciated from the following detailed description of a few specific embodiments shown in the accompanying drawings, in which:

Figure l is a diagrammatic view of an elemental iorm of the invention;

Figure 2 is a preferred form of the invention in which the relative motion between the sensing element and the controlling element is independent ci the desired control;

Figure 3 is a sectional View of a preferred type of controilin element, the section taken along the control path;

Figures 4 and 5 are similar views of alternative forms of controlling elements;

Figure 6 is a combined diagrammatic showing and circuit oi that form of the invention in which the displacements of the sensing element in following an arbitrarily contoured controlling element are utilized to effect the desired control; and

Figure 7 is anenlarged view ci the controlling element of Figure 6 shown in section with the sensing element.

In Figure 1 there is shown an elemental form of the invention. Endless steel tape i0, appropriately supported on pulleys, is moved through the air gap of C shaped core I2 by means of motor I4. When coil I6 surrounding core I2 is excited from an A.C. source, diierent voltages Will appear in coil I8, which also surrounds core I2, by virtue of the mutual induotance of the coils. The voltage differences depend on the magnetic reluctance or on the magnetization of the substance in gap 2) of core I2, and on the incremental permeability of the core. A certain voltage will be induced when a magnetically saturated part 215i (Figure 3) of tape I lies in gap '29. A higher voltage will be induced when an unmagnetized portion of tape IU passes through gape 20. The voltage induced in coil I8 is ampliiied, rectified if necessary, and the electrical output differentials are applied to the load.

The A.O. excitation of coil l5 should be of a relatively low intensity to avoid demagnetization of the saturated portions of tape I0. Coil l may consequently be energized at a high level (and preferably at' a higher frequency) should it be desired to obliterate the magnetized control portions of tape I6. By switching coil le to an appropriate D.C. source for critical time intervals While motor I4 feeds tape III at a uniform rate, a new arbitrary cycle may be established.

The control effected by means of the foregoing embodiment of the invention is ordinarily of an on-off nature. It is useful for controlling short cycles, such as traflic light sequences where the reestablishment of new timing sequences is frequently desired. For an extended sequence, a length of wire unwound from one reel and wound onto another can be used in place of the endless tape shown.

The foregoing embodiment relies on a change in mutual inductance of coils I5 and I8 for changing output as magnetic differences are successively introduced at gap 2B. The result is the same whether a uniform tape variably magnetized is used (Figure 3) or the tape has various cross-sections of magnetic material, homogeneous as in Figure 5, or with a non-magnetic support as in Figure 4. The same result can also be realized in reliance on the changing self-inductance of coil I8 on core I2, by incorporating coil I8 in an A.C. excited bridge and utilizing the unbalance changes that occur when magnetic differences are successively introduced at air gap 20. When using this bridge circuit, coil It can be connected in series with coil I8 or simply disconnected.

In Figure 2 there is shown a second form of the invention. In this form, a number of pickup heads are arranged to sense a corresponding number of tracks on a disc, not only establishing a timing sequence thereby, but also determining the relative timing of multiple components in a system.

Plural pickup heads may be used to control, as an example, the valves which determine the proportions of multiple fluids feeding into each batch of a mixture. The relative arcuate extents of magnetization in the respective tracks control the proportions of the mixture. The rate of travel of the controlling element relative to the pickup heads is varied to adjust the total volume of each batch.

The several control tracks may equally well be arranged to control multiple motors or clutches in an automatic machine tool. In order to prepare the magnetic control element foruse in this application, the machine tool is cycled manually to produce a given workpiece, at the same time energizing the magnetizing control related to the clutch or motor which, in automatic operation, would perform that function. Having operated a tool through an idle stroke, such as displacing the tool carriage of a lathe preparatory to calipering the work, the unnecessary magnetizing control may be eradicated by simultaneously energizing the magnetizing head with obliterating alternating current and reversing the travel of the magnetic control. The same procedure may be followed to correct errors in the controlling element, and to establish new control sequences. When a single perfect magnetized controlling element has been formed, it may be arranged to control the cycle of multiple automatic machines like that which was manually cycled in its preparation.

In Figure 2, plural pickup heads MI and 63 include cores d2 and 42' of a highly permeable magnetic material, such as mumetal, and shaped to constitute a closed magnetic circuit except for a gap for receiving the magnetic controlling element. In this embodiment of the invention, the controlling element is in the form of a disc 44 in which there are incorporated plural endless control tracks 45, 45', etc., one for each pickup head 40, Ml', etc. Disc All is carried by shaft 48 which is rotated by means of the schematically represented motor and reduction gearing unit 5B, which should include reversing and speed controls not shown.

On cores 42 and 42 there are center-tapped windings 54 and 54', the imp-edances of the halves of which are made equal at the excitation frequency. To compensate for secondary errors in matching the coil halves, a shunt trimming impedance may be used, such as variable condenser 55. The two halves of each winding 54 and 54 are a A.C. driven by center-tapped transformer` 58 `at a frequency equal to or higher than conventional power frequencies. Those halves are so connected in series that their separate responses due to a strong magnetic field introduced in the gap of core 42 or 42 will be additive in the center-tap circuit. That circuit in the present case is a transformer 69 connected at its primary between the center-tap of coil 5d and-the center-tap in the secondary of transformer 58.v

The cross-sectional dimensions of cores @2 and 42 are made small compared with the magnetic circuit length; and when this is done and sufficient A.C. drive is applied in the presence of a unidirectional magnetomotive force in the core, there will be a strong second harmonic voltage developed across the primary of transformer Bil. Other even harmonics will also be prominent but the output signal-to-noise ratio is greatly enhanced when only the strongest harmonic, the second, is filtered from the others. A second harmonic filter and amplifier E2 is connected to receive its input from the secondary of transformer 5B and is connected at its output side to a demodulator, or combined rectifier and low-pass lter 64. The function of unit 64 is to suppress the high frequency components due tothe A.C. excitation and to extract the relatively slower changes due to the magnetic condition of the control tracks. The electrical output of unit 64 may be utilized to control or even operate load 86.

Each of the sensing elements or pickup heads di), il, etc., will naturally have associated with it some form of detector or analyzer 56--64 which will determine its magnetic condition as affected by the control element M.

In applications described above, the detected output is utilized to e-ilect on-off control of electromechanical apparatus, such as valves, relays, etc. Additionally, varying-degrees of response of the pickup head can be obtained when associated with an appropriato controlling element to elect various degrees of control. Thus, in theatre lighting a dimmer can be variably operated by an electromagnet and restored by a spring under control of the foregoing apparatus.

It is sometimes necessary to eiect three levels of control, rather than all degrees of control or simply an on-off control. This is attainable in accordance with the present invention by utilizing opposite polarities of magnetization on the controlling element, as well as unmagnetized area. Coil 52 on core 42 is then biased with direct current to counterbalance the effect in the core of one polarity of magnetization, to yield zero output at transformer Eil. With unmagnetized portions of track l5 opposite core 52 there is a second level of output at transformer di? due to the bias current; and with the other polarity of magnetization in track 46. augmented by the D.C. bias, a third level of output is to be expected at transformer 60.

A permanently formed control track or either type shown in Figures 4 and 5 can be used in the apparatus of Figur-e 2. The track may be inagnetized or not; and where it is uninagnetised, use of the D.C. bias coil $2 with the secondharmonic type of detector will be found meritorious.

With the type of sensing element and detector shown in Figure where practical operation is dependent on a signicant degree oi coro saturation, it will be found that means in addition to the sensing head are required for obliterating and for remagnetizing control tracks d5. For this purpose an additional core coil are provided, with means to shiit it into the effective position of the sensing core and coil. Thus the entire sensing head 13 is shown mounted for sliding radially of disc te as a unit with heavy core 68'. The assembly is normally against stop 1G by spring 'l2 to maintain the jaws of core 52 opposite track 155. Solenoid it, energized D.C. source 'i8 through switch it, may be operated to shift the combined obliterating, magnetizing, and sensing head as a unit, moving core E8 against stop Sil and thereby positioning the jaws oi core 8 opposite track 45. Coil 82, einbracing core may then be A.-C. enereimd to establish a relatively high number of a -rcturns, preferably at a high frequency for obliterating the previous magnetization. Coil 82 is subsequently energized with D.-C. (of appropriate polarity if this is signiiicant) at the necessary intervals during the travel of disc lo to establish a new control sequence. If an error is made, the rotation of drive E@ may be reversed and coil S2 concurrently connected to the A.C, source for the necessary interval; and forward drive and controlled magnetization may then be resumed.

lThe obliterating and magnetizing components have been omitted from Figure 2 in showing sensing head 49 in the interest of clarity; but it to be understood that an obliterating and remagnetizing head will usually complement each sensing head.

Where a control trackl of the type shown in Figure 4 is used wherein the magnetic portions are of magnetic ink, the control sequence can be 'iii altered by removing the ink with a solvent-soaked roller and inscribing new control portions.

In the form of the invention shown in Figure 6 the output of the detector is, as in other forms, dependent on the interaction between a sensing head and a magnetic controlling element. The detector output in this form is utilized to control a servornctor for displacing the sensing head to track a magnetic template or pattern in such direction as to maintain sensibly constant detector output. The mechanical output oi the servomotor is also used for eiecting external control or external drive.

The specific form illustrated in Figure 6 includes a soft iron disc |00 supported and rotated at a uniform rate by means of motor and reduction gearing unit |92. Secured to the upper surface of disc |35 is an arbitrarily contoured loop |35 of soft iron. Its cross-section is generally rectangular so that it may rest flat on disc l'li, but its upper surface is somewhat convex (Figure '7).

U shaped magnetic cores |66 and |63 are inverted and secured to each other to form a double U with a magnetic insulator IIQ between the adjacent arms. The double U is arranged with its center arm over loop |04, this arm being shortened so that the outer arms may be close to disc A center-tapped coil H2 embraces cores H15 and Hill and is A.-C'. excited by means of center-tapped transformer I4.

The transformer secondary and coil H2 constitute a balanced bridge when magnetic insulator H0 is aligned with the median of loop 94. Should insulator |55? be displaced laterally er" loop ISLE, there would be a change in impedance, resulting in a sharp phase shift in the output or" the bridge. This output is optionally filtered in phase-compensated preamplier IIE, and applied by amplifier i i3 through transformer |2il to one phase iZfl of two-phase motor 22. A cond phase 25 oi' motor |22 is energized from the same source as that which is used to energize transformer I4.

Motor |22 can in some cases be utilized to shift the sensing head as required to trace ioop iift during the rotation or dise H39. But because its mechanical output (for a reasonable size of motor |22 and control source of supply |if, H3, |29) is inadequate for most purposes, motor |22 is used in the device illustrated in Figure 6 as a phase-sensitive device for controlling the valve of a hydraulic motor which in turn drives both the sensing head and the eX- ternal load as determined by the contour of loop it.

Motor |22 is connected through a suitable linkage |28, |29, |39 to the slide E32 of a fluid valve i3d. When slide $32 is displaced in one direction or another from center, it admits huid under pressure from line itil as supplied by pump iet* to one end or the other of uid motor |45. rEhe fluid from the low pressure side of motor i-E is returned through line |34 or |35 to sump idf? by way of line ilS. When slide |32 is centered, the pressure built up by pump Mt is bypassed by relief valve |42, the fluid returning to sump |136,

Piston |138 of fluid motor |45 has a rod |53 'which not only displaces the sensing head ramady ci disc i to the extent required by the contour of loop i but additionally displaces arm E 52, ia'hich is the tais.. oii for controlling or driving the external load. In common with other servo systeme, it will be understood that some form of oscillation damper tol be incorporated in the electrical or hydraulic portion of the organization; and limited damping action may be realized through careful design of the center arm of the double U and of the cross- Y of the mutually perpendicular double Us arev shifted along a trace such as we. Alternatively the composite head may be fixed, and the pattern may be shifted by the servo actuators. Such systems eliminate drive unit m2. Either form is useful for controlling a flame cutter or other tool, the function of which is to duplicate the shape of the control pattern.

Other forms of control pattern than that illustrated in Figure 6 may replace that shown and described. For example, a sheet-iron cutout can be used; or a trace magnetized perpendicular to the face of disc IGS (see Figure 3). Each of these alternatives involves judicious modification of the pickup head or a substitution of another form such as is shown in Figures l and 2.

What I claim is:

l. A controlling device comprising a controlling element having a pattern of magnetically different parts, a sensing element, means distinct from and in addition to said controlling element to energize said sensing element periodically, driving means to cause said sensing element to coact with any particular one of said parts at any particular time, and a detector differently responsive to the coaction of said different parts with the sensing element.

2. Apparatus according to claim l wherein said driving means causes said sensing element to travel relatively along a predetermined path including said magnetically different parts.

3. Apparatus according to claim l including a servomotor controlled by said detector for moving said sensing means at an angle to said relative travel and for correspondingly moving an external load.

4. A device for operating electrical apparatus comprising a controlling element having a pattern of magnetically diierent parts, means differently responsive to said magnetically different parts for operating said apparatus, said means including a sensing element and means distinct from and in addition to said controlling element and any effect of said controlling element for exciting said sensing element with varying current, and a drive establishing coaction of said sensing element relative to any particular predetermined one of said parts at any particular time.

5. A device according to claim 4 in which certain of said parts are permanently magnetized.

6. The method of providing an automatic equipment-control sequence comprising the steps of magnetizing a control member in a predetermined pattern so as to be magnetically different at different parts corresponding to the required rcontrol sequence, moving said member past a sensing device of the undulatory current type, and exciting said device at a frequency that is high relative to the highest rate of traverse of the different parts past the sensing device.

7. A device for operating electrical apparatus, including a controlling element having a pattern of magnetically different portions, detecting means differently responsive to said differentv portions, said detecting means having a sensing element having a magnetic core in apposition to said controlling element and means separate and distinct from said controlling element and 'of the motion thereof for producing repetitive magnetic variations in said core, and means for bringing a deiinite predetermined portion of said controlling element into coactive relationship with said sensing element at any given time.

8. A load controlling device including a variously magnetized control element, means for sensing and detecting the magnetization of a local area thereof, said sensing and detecting means including a core for coaction with said control element and means distinct and independent of said control element for repetitively varying the magnetic condition of said core, and means for bringing a definite predetermined portion of said control element into cooperation with said core at any particular time.

9. A control device including a multiple-track controlling element, each track of which contains portions of differing magnetic characteristics, means associated with each track responsive to said magnetic characteristics for controlling a respective apparatus component, said responsive means including means separate and distinct from the controlling element, and from the motion thereof, causing regularly repetitive magnetic variations in the portion thereof that coacts with said associated track, and means establishing coaction of a predetermined portion of said controlling element with said responsive means.

10. Apparatus for operating an electrical device, comprising a controlling element having a control track of magnetically different portions, combined sensing and detecting means differently responsive to diierently magnetized portions for controlling said device, said combined means having a coil and core in intimate magnetic relationship with said controlling element and alternating current exciting means for said coil separate and distinct from said controlling element or the motion thereof, and means to locate particular portions of said controlling element in cooperative relationship with said core in definite, predetermined succession.

11. Apparatus for operating electrical equipment comprising a track of magnetic material only portions of which are magnetized, means differently responsive to magnetized and unmagnetized portions for controlling said equipment, said means including a saturable-core pickup head and means for periodically varying the magnetization thereof, and a mechanical drivefor positioning successive portions of said track opposite said pickup head.

l2. Apparatus for controlling an electrical device comprising a control track of magnetic material having magnetized portions, means including a saturable-core pickup head and means for periodically varying the magnetization thereof for controlling said device according to a predetermined time sequence, a mechanical drive for moving said pickup head relatively along said track, an alternative head for modifying the magnetization of said track to establish a new time sequence, and means for interchanging said pickup head and said alternative head With respect to said track.

13. A program control comprising, in combination, a track having successive magnetically dierent portions, a core adjacent to the track, a drive for causing relative motion between said core and said track along the latter, a source of regularly varying magneto-motive force for exciting said core, and means for detecting differences in the eiiect of said magneto-motive force on said core as diierent portions of said track are opposed to said core in succession.

14. A device for operating electrical apparatus comprising a control track of magnetic material having magnetized portions, means differently responsive to parts of different magnetization for operating said apparatus, said means including an alternating current excited sensing element and alternating-current exciting means for said sensing element distinct and independent of the control track and of the motion thereof, and means for moving said element relatively along said track in a predetermined time schedule.

15. A contour tracer including a body incorporting a magnetically distinctive contour, means differently responsive to magnetic differences including a sensing element including a magnetic core and means separate and distinct from said contour or the motion thereof for producing magnetic variations in said core, said core coacting with said contour, and an actuator controlled by said responsive means for maintaining said sensing element in predetermined proximity to .Said contour.

16. Apparatus for controlling a machine component comprising a magnetic pattern, a. pickup head having a magnetic core and internal means repetitively varying the magnetic condition of said core, means :for determining the response of the pickup head to the opposed portion of the pattern, a driver for moving the pickup head relatively along the surface of the pattern in one coordinate, and means for maintaining the pickup head adjacent the edge of the pattern by moving it in another coordinate relative to the pattern and for operating the machine component.

17. A pattern follower including a magnetic pattern, an alternating current excited coil having a magnetic core, means critically responsive to the coaction of the core with the contour outline, an actuator controlled by said responsive means for moving the core relatively toward the pattern outline, and other means for moving the core relatively along the pattern outline.

18. Apparatus for operating a machine component, comprising a coil having a magnetic core, an alternating current bridge including said coil in one of its arms, a magnetic contour. means for moving the core relatively along the contour, and an actuator for moving the core relatively toward the contour and for operating said machine component, the actuator being controlled by the output circuit of the bridge.

19. Apparatus for operating an electrical load,

including a track of magnetic material only portions of which are magnetized, a sensing element located at a sensing position, means for moving said portions of said track past said sensing element according to a predetermined time schedule, and means separate and independent of said control element for introducing repetitive magnetic variations in said sensing element at a repetition rate that is high in relation to the rate of traverse of said portions past said sensing element.

20. Apparatus for operating an electrical load, including a track of magnetic material only portions of which are magnetized, a sensing element located at a sensing position, drive means enforcing deinite predetermined sensing relationship of any particular portion of said track opposite said sensing element at any given time, and means producing a plurality of repetitive magnetic variations in said sensing element during the time that any particular one of said portions is in sensing relationship to said sensing element.

21. Apparatus for operating an electrical load, including a member embodying a track having discrete magnetized and unmagnetized areas, sensing means located at a sensing position including a saturable core oriented in sensing relation to said track, motive means establishing a predetermined sensing relation of one of said areas opposite said core at any particular time, and electrical exciting means varying the saturation of said core a plurality of times during the period that any one of said areas remains in sensing position.

22. A load controlling device in accordance with claim 8 wherein said control element embodies unmagnetized portions and portions of opposite polarities of magnetization.

23. A load controlling device in accordance with claim 8 including an electromagnet for modifying the magnetization of said control element at diierent areas as may be brought into cooperation therewith.

GEORGE C. DEVOL.

REFERENCES CITED The following references are of record in the le of this patent: 

